# CloudHub Worker Recovery and Reliability

*MuleSoft Platform Architect Study Guide · Deploying API implementations to CloudHub · Last updated November 13, 2026 · https://www.certifyforce.com/study-guide/mulesoft-platform-architect/deploying-api-implementations-to-cloudhub/cloudhub-worker-recovery-and-reliability*

Predict classic CloudHub workload distribution, queue and connection behavior, and the recovery dependencies that constrain updates and regional plans.

- Certification: Salesforce MuleSoft Platform Architect
- Exam section: Deploying API implementations to CloudHub
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-platform-architect

**Official exam objective:**

> Given an app deployed to the CloudHub shared worker cloud in one or more regions, describe and predict its reliability and performance characteristics.

## What the exam expects

- Predict which work additional CloudHub workers can distribute.
- Separate persistent-queue protection from exactly-once delivery.
- Interpret waiting, in-flight and processed queue evidence before operating on a queue.
- Account for idle connections, update limitations and unavailable deployment services.

**Worker scale-out** adds independent runtime instances; **persistent queues** retain queued work; **in-flight** messages are being processed after a queue; an **idle timeout** measures a period without data; a **durable subscriber** can impose an exclusive external identity ([High availability](https://docs.mulesoft.com/cloudhub/cloudhub-fabric), [Queues](https://docs.mulesoft.com/cloudhub/managing-queues), [Networking](https://docs.mulesoft.com/cloudhub/cloudhub-networking-guide), [Runtime updates](https://docs.mulesoft.com/cloudhub/cloudhub-app-runtime-version-updates)). This lesson uses classic CloudHub workers.

## Key facts

| Fact | Detail | Source |
| --- | --- | --- |
| HTTP distribution | Requests distribute across assigned workers. | [HA](https://docs.mulesoft.com/cloudhub/cloudhub-fabric) |
| Batch distribution | One job runs on one worker at a time. | [HA](https://docs.mulesoft.com/cloudhub/cloudhub-fabric) |
| Delivery semantics | Persistent queues can deliver duplicates. | [Queues](https://docs.mulesoft.com/cloudhub/managing-queues) |
| HTTP-only workloads | Persistent queues are not required for load distribution. | [HA](https://docs.mulesoft.com/cloudhub/cloudhub-fabric) |
| In-flight work | Remains on the queue until processing completes. | [Queues](https://docs.mulesoft.com/cloudhub/managing-queues) |
| Clear | Flushes waiting and in-flight messages. | [Queues](https://docs.mulesoft.com/cloudhub/managing-queues) |
| Idle timeout | 300 seconds without data closes both connections. | [Networking](https://docs.mulesoft.com/cloudhub/cloudhub-networking-guide) |
| Durable subscriber | Exclusive identity can require manual stop/start for updates. | [Updates](https://docs.mulesoft.com/cloudhub/cloudhub-app-runtime-version-updates) |
| Recovery dependency | US East failure can block new deployments through the control plane. | [HA/DR](https://docs.mulesoft.com/cloudhub/cloudhub-hadr) |

## Check yourself

- Why is disabling persistent-queue encryption unsafe to treat as a future-write-only change?
- When counts change before the throughput thumbnail refreshes, which cadence difference explains it?
- When batch should stop using persistent queues while other components retain them, which setting scopes that change?

## Sources

- [CloudHub High Availability Features](https://docs.mulesoft.com/cloudhub/cloudhub-fabric)
- [Manage Queues](https://docs.mulesoft.com/cloudhub/managing-queues)
- [CloudHub Networking Guide](https://docs.mulesoft.com/cloudhub/cloudhub-networking-guide)
- [CloudHub Runtime Continuous Updates](https://docs.mulesoft.com/cloudhub/cloudhub-app-runtime-version-updates)
- [CloudHub High Availability and Disaster Recovery](https://docs.mulesoft.com/cloudhub/cloudhub-hadr)
- [Pinned CloudHub Queue Guide](https://raw.githubusercontent.com/mulesoft/docs-runtime-manager/5b945c7e4b051dabb480184d93217e7df2dde16a/cloudhub/modules/ROOT/pages/managing-queues.adoc)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 7 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Platform Architect pack (USD $19): https://www.certifyforce.com/practice-exams